Damage-associated endogenous molecules induce innate immune response, thus making sterile inflammation medically relevant. Stress-derived extracellular vesicles (stressEVs) released during oxidative stress conditions were previously found to activate Toll-like receptor 4 (TLR4), resulting in expression of a different pattern of immune response proteins in comparison to lipopolysaccharide (LPS), underlying the differences between pathogen-induced and sterile inflammation. Here we report that synergistic activities of 15-lipoxygenase (15-LO) and secreted phospholipase A₂ (sPLA₂) are needed for the formation of TLR4 agonists, which were identified as lysophospholipids (lysoPLs) with oxidized unsaturated acyl chain. Hydroxy, hydroperoxy, and keto products of 2-arachidonoyl-lysoPI oxidation by 15-LO were identified by mass spectrometry (MS), and they activated the same gene pattern as stressEVs. Extracellular PLA₂ activity was detected in the synovial fluid from rheumatoid arthritis and gout patients. Furthermore, injection of sPLA₂ promoted K/BxN serum-induced arthritis in mice, whereby ankle swelling was partially TLR4 dependent. Results confirm the role of oxidized lysoPL of stressEVs in sterile inflammation that promotes chronic diseases. Both 15-LO and sPLA₂ enzymes are induced during inflammation, which opens the opportunity for therapy without compromising innate immunity against pathogens.

与损伤相关的内源性分子诱导先天免疫反应，从而使无菌炎症在医学上具有相关性。先前发现在氧化应激条件下释放的源自应激的细胞外囊泡（stressEVs）激活Toll样受体4（TLR4），导致与脂多糖（LPS）相比，免疫应答蛋白的表达方式有所不同，这是两者之间的差异所在病原体引起的无菌炎症。在这里我们报告15脂氧合酶（15-LO）和分泌的磷脂酶A ₂（sPLA ₂）是形成TLR4激动剂所必需的，被鉴定为具有氧化的不饱和酰基链的溶血磷脂（lysoPLs）。通过质谱（MS）鉴定了15-LO氧化2-花生四烯酰基-lysoPI的羟基，氢过氧基和酮基产物，它们激活了与StressEVs相同的基因模式。在类风湿关节炎和痛风患者的滑液中检测到细胞外PLA ₂活性。此外，注射sPLA _2可以在小鼠中促进K / BxN血清诱发的关节炎，从而使踝关节肿胀部分依赖于TLR4。结果证实了stressEV的氧化lysoPL在促进慢性疾病的无菌炎症中的作用。15-LO和sPLA ₂ 炎症过程中会诱发酶，这为治疗提供了机会，而又不会损害针对病原体的先天免疫力。